Various methods and apparatus have been used to efficiently pump lasers and to get the maximum output from the laser pumping media. For example, U.S. Pat. No. 3,311,844 (DiCurcio) disclosed a "high-speed" pulsed laser system. It uses multiple rods that are secured to the periphery of a wheel. The rods are rotated into a laser cavity and pulsed pumped and fired. However, "high-speed" for this system is 1 Hz with very high power. Also embodied in this patent is cooling of the rods by a method of selective indexing. This system also shows that multiple pumping lamps can be used to pulse pump these one or more rods in the pumping chamber. These lamps are flashed in coordination with the passage of the rods through the pumping chamber to deliver pumping energy to the rod in the chamber. In this manner the lamps are fired sequentially to avoid excessive heat build-up in any one lamp. If it is desired to cool each laser rod after the rod has been pulsed, one or more cooling devices such as fans or blowers can be placed around the periphery of the system to deliver a flow of cooling air to cool the laser rods after they have been pulsed.
U.S. Pat. No. 4,567,597 (Mandella) discloses a laser system having a stationary lasing region. The lasing medium is rotated to bring thermally cooled unpumped portions into the lasing cavity and where it is pumped and then allowed to lase, and the lasing media is then rotated out of the lasing cavity so that heat is transferred out of the cylinder to the surroundings. This patent also discloses a laser rod in the shape of a hollow cylinder that is rotated so that the cooled and non-excited region is brought into the resonator cavity, is allowed to lase, the then fired portion of the hollow laser rod is rotated out so that heat is transferred out of the hollow cylinder to the surroundings.
U.S. Pat. No. 4,575,854 (Martin) discloses another unique pumping scheme for Nd:YAG lasers. Instead of using an arc lamp, a bank of laser diode arrays or an array of laser diodes surrounds the cylindrical rod. These laser diode arrays are sequentially pulsed to provide CW pumping, by insuring that at least one diode array is on while the others are off. Each diode array actually operates at quite a low duty-cycle for cooling purposes. The stationary Nd:YAG laser rod is pumped by the surrounding array of diode laser bars, which are electronically fired in rotation.
U.S. Pat. No. 4,845,721 (Hoffmann) discloses a solid state laser rod having internal bores through which a coolant can flow. Hoffmann also discloses rotating the rod so that only specific portions of the laser materials are subjected to pumping while other portions are cooling. This patent also describes means by which solid-state laser media can be cooled through special designs/shapes of the actual material. These designs facilitate laser cooling by increasing surface area for heat extraction. Reference is made to a tubular shaped rod (empty cylinder) which is rotated into the resonator pumping region, however, this is done solely for cooling purposes.
U.S. Pat. No. 4,890,289 (Basu et al.) discloses a rotating disk laser which is optically pumped by a source positioned off center from the axis of rotation of the lasing disk. This patent describes both rotation or translation of the lasing medium for the purpose of thermal load distribution. Reducing the thermal effects caused by lamp pumping is the main purpose of this patent. It incorporates diode-pumping with delivery of that radiation via fiber optics. Additionally, the rotation of the medium is solely for the purpose of reducing thermal stress in the medium.
This invention, however, discloses a spinning beam steering assembly (SBSA) that is spun at high rates of speed on its axis. The SBSA offsets the lasing optical path, and causes the lasing path to be swept through a circular region of the lasing medium. The output laser beam remains stationary on the SBSA's spin axis. The size of the lasing medium should be slightly larger than the size of the circular region swept by the SBSA. While the SBSA is spun, within the laser cavity, the lasing medium is pumped with energy. The off-axis beam of light swept by one or more SBSA is then amplified by the rod and transmitted through at least one end mirror and is then directed to the work-piece.
The spinning beam steering assembly increases the laser repetition rate, because as the SBSA spins, the swept area of the lasing medium that is not releasing energy or photons or not lasing is being charged or pumped with energy or photons, so that each area that lases is fully charged when it is allowed to lase through the SBSA.
Additionally, for the maximum repetition rates of this invention and for repetition rates less than the higher repetition rate of the current invention, all laser pulses will have uniform intensity, because the area swept by the SBSA will be fully pumped or charged (saturated) and ready to lase. This results in uniform pulse intensities through the full range, i.e., from very low repetition rates to the new higher repetition rates for a laser, which is greatly desirable for many laser applications.